China has ordered mosques in its restive western city of Urumqi not to open for Friday prayers.
The order comes after several days of ethnic violence between Uighur Muslims and Han Chinese. At least 156 people have been killed so far.
Thousands of troops remain in Urumqi, the capital of Xinjiang province, to try to maintain order.
The Chinese authorities have vowed to administer "severe punishment" to those involved in the riots.
An unnamed government official told the Associated Press news agency that people in Xinjiang should "stay at home and pray", rather than gathering in mosques.
The official said the order had been given on public safety ground.
The violence began on Sunday when Uighurs rallied to protest against a deadly brawl between Uighurs and Han several weeks ago in a toy factory in southern Guangdong province.
Security has been high in the city since the recent unrest
Officials say 156 people - mostly Han - died in Sunday's violence.
Uighur groups say many more have died, claiming 90% of the dead were Uighurs.
More than 1,400 people are thought to have been detained.
On Thursday, China said it had "a great deal of evidence" that some of those involved in the violence had "training from foreign terrorist groups including Al-Qaeda".
Foreign ministry official Qin Gang did not say what the evidence was, but said the groups were "inextricably linked with three vicious forces from abroad".
Tensions have been growing in Xinjiang for many years, as Han migrants have poured into the region, where the Uighur minority is concentrated.
Many Uighurs feel economic growth has bypassed them and complain of discrimination and diminished opportunities.
BBC NEWS | Asia-Pacific | China bans Urumqi mosque prayers
